Molecular Dynamics Simulations of Heterogeneous Hydrogen Bond
Environment in Hydrophobic Deep Eutectic Solvents
Abstract
Hydrophobic deep eutectic solvents (DESs) have emerged as excellent
extractants. Their performance depends on the heterogeneous hydrogen
bond environment formed by multiple hydrogen bond donors and acceptors.
An understanding of this heterogeneous hydrogen bond environment can be
used to develop principles for designing high-performance DESs for
extraction and other separation applications. We investigate the
structure and dynamics of hydrogen bonds in eight hydrophobic DESs
formed by decanoic acid, menthol, thymol, and Lidocaine using molecular
dynamics simulations. The results show the diversity of hydrogen bonds
in the eight DESs and their impact on diffusivity and molecular
association. Each DES possesses four-six types of hydrogen bonds and one
or two of them overwhelm the others in quantity and lifetime. The
dominating hydrogen bonds determine whether the DESs are governed by
intra- or inter-component associations. The component diffusivity
presents an inverse relationship with the hydrogen bond strength.